Question: what is the locomotive class has the highest  boiler pressure?
Paraphrase: What category of locomotives have higher pressure in the boiler?
SPARQL (Wikidata): select ?ent where { ?ent wdt:P31 wd:Q19832486 . ?ent wdt:P5071 ?obj } ORDER BY DESC(?obj)LIMIT 5 
Answer: Norfolk and Western Railway class J, Great Northern Railway N-3, Great Northern Railway S-1, Great Northern Railway O-8, Great Northern Railway R-2